An emotional Sheriff Joseph Lombardo offered updates Friday into the deadliest mass shooting in modern American history.

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At a Las Vegas news conference, Lombardo affirmed the number of dead at 58, and the number of injured at 546. 501 of those injured victims have been treated and have left area hospitals, while 45 remain hospitalized.

Lombardo says an autopsy has been performed on gunman Stephen Paddock, adding that "no visual abnormalities" were discovered in the shooter's brain. Additional testing is expected and the brain has been sent to another facility for further testing, according to authorities.

At this time officials still haven’t determined Paddock's motive. FBI Special Agent in Charge Aaron Rouse says investigators have found no signs that Paddock had ideologies or connections to any groups.

Lombardo also shed light on reports that Paddock fired rounds at fuel tanks at Las Vegas' McCarran International Airport. The sheriff says the airport is reviewing safety measures and has contacted experts in fuel storage but that there’s a low probability aviation fuel could be ignited by gunfire.

Lombardo also said he was "absolutely offended" at accusations that Las Vegas authorities were incompetent after questions about the timeline of the shooting were raised. The sheriff said he stands by their timeline, which has been disputed by the hotel where the gunman opened fire.

Lombardo told reporters Friday that Paddock rained down bullets on a concert crowd starting at 10:05 p.m. Oct. 1. He has said that six minutes earlier, Paddock sprayed 200 rounds from his Mandalay Bay hotel room into the hallway, hitting a security guard in the leg.

That timeline released earlier this week differed from a week ago, when authorities said the guard was shot after Paddock opened fire on the crowd.

The changes led to questions about why police and hotel security weren’t able to stop Paddock sooner.

Mandalay Bay officials have disputed whether six minutes actually passed between the first gunfire in the hallway and the start of the concert rampage.